Nitric oxide fragments

Photochemical elimination reactions include all those photoinduced reactions resulting in the loss of one or more fragments from the excited molecule. Loss of carbon monoxide from type I or a-cleavage of carbonyl compounds has been previously considered in Chapter 3. Other types of photoeliminations, to be discussed here, include loss of molecular nitrogen from azo, diazo, and azido compounds, loss of nitric oxide from organic nitrites, and loss of sulfur dioxide and other miscellaneous species. 

These compounds contain the fragment R as an alkyl or aryl moiety. In other words, they result from the esterification of an alcohol or a phenol with nitrous acid, nitric acid, phosphoric acid, sulfuric acid, or sulfamic acid, respectively. Many of the esters to be examined in this chapter must be activated prior to eliciting their effects, e.g., the organic nitrites and nitrates, which act as donors of nitric oxide or an analogous molecule, and phosphates, which are activated by hydrolysis or even by phosphorylation (antiviral agents). Sulfates are very seldom active or used as prodrugs, but they have significance as metabolites and as industrial xenobiotics. 

Chemical radicals—such as hydroxyl, peroxyhydroxyl, and various alkyl and aryl species—have either been observed in laboratory studies or have been postulated as photochemical reaction intermediates. Atmospheric photochemical reactions also result in the formation of finely divided suspended particles (secondary aerosols), which create atmospheric haze. Their chemical content is enriched with sulfates (from sulfur dioxide), nitrates (from nitrogen dioxide, nitric oxide, and peroxyacylnitrates), ammonium (from ammonia), chloride (from sea salt), water, and oxygenated, sulfiirated, and nitrated organic compounds (from chemical combination of ozone and oxygen with hydrocarbon, sulfur oxide, and nitrogen oxide fragments). ... 

In the presence of various metal ions, 2-(fluoroenone)benzothiazoline has been found to rearrange to A-2-mercaptophenylenimine, while a free radical mechanism involving the homolysis of C-S and C-N bonds has been invoked to explain the formation of 3-phenyl-1,2,4-triazole derivatives from the thermal fragmentation and rearrangement of 2-(arylidenehydrazino)-4-(5//)-thiazolone derivatives. The cycloadducts (36) formed from the reaction of 3-diethylamino-4-(4-methoxyphenyl)-5-vinyl-isothiazole 1,1-dioxide (34) with nitric oxides or miinchnones (35) have been found to undergo pyrolytic transformation into a, jS-unsaturated nitriles (38) by way of pyrrole-isothiazoline 1,1-dioxide intermediates (37). 

NC is an energetic nitropolymer consisting of a hydrocarbon structure with -O-NO2 bonds as oxidizer fragments. In general, NC is produced from the cellulose, C6H702(0H)3 j of cotton or wood, which is nitrated using nitric acid (HNO3) to introduce -O-NO2 bonds into its structure. 

IV) Dark zone In this zone, oxidation reactions of the products formed in the fizz-zone reaction take place. Nitric oxide, carbon monoxide, hydrogen, and carbonaceous fragments react to produce nitrogen, carbon dioxide, water, etc. These exothermic reactions occur only very slowly unless the temperature and/or pressure is sufficiently high. 

Ji, H.T., Stanton, B.Z., Igarashi, J., Li, H.Y., Martasek, P., Roman, L.J., Poulos, T.L., Silverman, R.B. Minimal pharmacophoric elements and fragment hopping, an approach directed at molecular diversity and isozyme selectivity. Design of selective neuronal nitric oxide synthase inhibitors. J. Am. Chem. Soc. 2008, 130, 3900-14. 

Harteck and Dondes studied the decomposition of NO by the impact of fission fragments of 235U, and obtained a value of 1.9 x 108 M 1 sec-1 for kig. Kistiakowsky and Volpi used a flow discharge system to react active nitrogen with nitric oxide and studied the products in a mass spectrometer. However, they found the reaction to be too rapid for quantitative measurement and put a lower limit of 4 x 10 M 1 sec 1 on kig. A year later,254 they extended their work and were able to raise the lower limit to 5 x 1010. This result depended on the validity of the stirred-reactor approximation. 

The processes going on inside this ceramic catalytic converter include the reactions shown in the insert. Fragments of unburned hydrocarbons and carbon monoxide and nitric oxide molecules are converted to less noxious substances, such as nitrogen and carbon dioxide, by reactions at the surface of the catalyst. 

Nitric oxide as a reagent gas for the Cl has been proposed by Hunt and Harvey111. The ions mlz 30 (NO+) and m/z 60 ([NO NO]+) react with internal olefins and dienes to produce (M + NO)+, M+ and (M — 1)+. Terminal olefins produce in addition a series of fragments derived from the Markownikoff addition of NO+ to the olefin linkage. This... 

No molecular ions appear in the electron ionization (El) spectra of mesoionic 1,2,3,4-oxatriazoles 4 and 6 or their derivatives. Instead, [M+ —30] peaks are observed due to loss of nitric oxide <1979J(P1)747, 1999CHE363>. The typical fragmentation pathway for such compounds and their analogues is summarized in Scheme 1 <1984CHEC(4)579, 1996CHEC-II(4)679>. In their fast atom bombardment (FAB) spectra, intact molecular ion peaks are observed for the A2-l,2,3,4-oxatriazolines 23 114 [M+H] and 24 142 [M+H] <2002HAC307>. 

The practical motivation for understanding the microscopic details of char reaction stem from questions such as How does the variability in reactivity from particle to particle and with extent of reaction affect overall carbon conversion What is the interdependence of mineral matter evolution and char reactivity, which arises from the catalytic effect of mineral matter on carbon gasification and the effects of carbon surface recession, pitting, and fragmentation on ash distribution How are sulfur capture by alkaline earth additives, nitric oxide formation from organically bound nitrogen, vaporization of mineral constituents, and carbon monoxide oxidation influenced by the localized surface and gas chemistry within pores ... 

Similar observations on the role of CDases were also obtained in rat renal mesangial cells stimulated with TNFa or nitric oxide donors. Both of these agonists were shown to stimulate sphingomyelinases, but only nitric oxide donors inhibited CDases and resulted in an increase in Cer levels and DNA fragmentation (Huwiler et al., 1999). 

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